The present invention relates generally to herbicidal concentrate compositions, processes for preparing these concentrates, and methods of using such compositions to kill or control the growth and proliferation of unwanted plants. In particular, the present invention relates to herbicidal concentrate compositions which comprise a salt of N-(phosphonomethyl)glycine(glyphosate) and a salt of 3,6-dichloro-2-methoxy benzoic acid (also known as 3,6-dichloro-o-anisic acid and commonly referred to as dicamba).
Glyphosate is well known in the art as an effective post-emergent foliar-applied herbicide. In its acid form, glyphosate has the following structure:
Glyphosate acid is relatively insoluble in water (1.16 wt. % at 25° C.). For this reason it is typically formulated as a water-soluble salt. For example, herbicidal concentrate compositions and application formulations containing the sodium, potassium, ammonium, isopropylamine, or monoethanolamine salts of glyphosate are well known in the art.
Herbicidal compositions and formulations comprising glyphosate or salts thereof are useful for suppressing the growth of, or killing, unwanted plants such as grasses, weeds and the like. Glyphosate is typically applied to the foliage of the target plant. After application, glyphosate is absorbed by the foliar tissue of the plant and translocated throughout the plant. Glyphosate noncompetitively blocks an important biochemical pathway which is common to virtually all plants, but which is absent in animals. Although glyphosate is very effective in killing or controlling the growth of unwanted plants, the uptake (i.e., absorption) of glyphosate by the plant foliar tissue and translocation of glyphosate throughout the plant is relatively slow. Visual symptoms that a plant has been treated with glyphosate may not appear until one week or more after treatment.
Dicamba has proven to be a particularly effective auxin herbicide. In its acid form, dicamba has the following structure:

Like glyphosate, dicamba is typically formulated as a salt, such as a sodium, potassium, diethanolamine, isopropylamine, diglycolamine, or dimethylamine salt.
Generally, auxin herbicides such as dicamba mimic or act like natural auxin plant growth regulators. Auxin-like herbicides appear to affect cell wall plasticity and nucleic acid metabolism, which can lead to uncontrolled cell division and growth. The injury symptoms caused by auxin-like herbicides include epinastic bending and twisting of stems and petioles, leaf cupping and curling, and abnormal leaf shape and venation.
Off-site movement is commonly associated with dicamba and other auxin herbicides. Under certain conditions of application, dicamba can migrate from the application site to adjacent crop plants, such as soybeans and cotton, where contact damage to sensitive plants can occur. Various strategies have been suggested to reduce off-site movement of dicamba including formulating dicamba in the form of certain mineral or amine salts, encapsulating dicamba with a polymeric coating, and complexing with a polybasic polymer.
With the development of transgenic plants including stacked glyphosate-tolerant and dicamba-tolerant traits, herbicidal compositions containing a combination of glyphosate and dicamba are particularly beneficial and convenient for control of unwanted plants. There is a need for highly concentrated herbicidal compositions containing glyphosate and dicamba that can be economically produced while having sufficient stability and that can be diluted to provide effective spray formulation solutions for application to unwanted plants.
As will be clear from the disclosure that follows, these and other benefits are provided by the present invention.